The invention relates to a casing for a hinge attachment of a car seat with a first hinge part firmly connectable to the frame of the back of the seat, a second hinge part firmly connectable to the frame of the seat, wherein the hinge parts, with respective perpendicularly bent off edges abutting each other at their front ends and symmetrically arranged with regard to the hinge axle with formed hollows, form the casing, a toothed element belonging to the casing, the toothing of which at least extends over one segment of the circle and is radially directed to the inner side, and a clamping ring holding together the edges of the hinge parts.
The invention further relates to a method for manufacturing a casing for hinge attachments of a car seat, wherein the hinge parts and a toothed element are largely brought into their final shape by fine blanking and forming, especially by hobbing and drawing, and matched according to dimensions thereof.
Conventional seat adjustment components, e.g. fixed and swivelling hinge parts of hinge attachments, are produced by forming and fine blanking or precision blanking with high dimensional accuracy regarding the finally intended use. These hinge parts have internal toothings or external toothings transmitting rotational movements, which are formed in one piece by ejection (see, for example, DE 32 44 399 C2, DE 28 34 492 C2, DE 32 27 222 C1).
The known state of the art according to DE 32 44 399 C2 attempts to control the minimum dimension of the effective toothed areas necessary for transmitting the rotational movement and the load from one hinge part to the other hinge part by using, for fine blanking, a bigger crimp area than necessary for the ejection area, so that the surplus material to be crimped serves for broadening the respective effective toothed area in excess of the thickness of the source material. This leads to a minor broadening of the teeth in excess of the source material but also to an attenuation of the material between crimped and ejected area. Therefore, fractures in the event of sudden loads cannot be excluded.
Moreover, no significant reductions of the effective thickness of the hinge parts can be achieved, because the crimped area always is limited to the toothed area.
Moreover, in the case of very fine toothings, as is necessary for a continuous and jerk-free adjustment of the back, fine blanking reaches its technological limits.
The limitations of fine blanking of portions with small corner radii in relation to the thickness of the sheet to be cut and to the quality of the material are well known. Based on experience, a fine blanking severity is defined which distinguishes the severity degrees S1 (easy), S2 (medium) and S3 (difficult) (see “Umformen und Feinschneiden”, in Handbuch für Verfahren, Werkstoffe, Teilegestaltung, pages 154 to 165, Verlag Hallwag AG, 1997, Switzerland). Thus the severity degree is essentially defined by the cutting path geometry and the thickness of the metal sheet. For this, the cutting path geometry is divided into simple geometric basic areas such as corner radii, hole diameters, groove and fin widths. From the ratio between a geometric dimension and the thickness of the metal sheet results the severity degree of fine blanking, which grows with growing metal sheet thickness.
This means that obtuse-angled corners with big radii are to be cut better than sharp-cornered with small radii.
Moreover, EP 0 694 434 B1 discloses a hinge for a car seat. This hinge includes a first flange and a second flange, wherein the first flange is firmly connectable to the frame of the back of the seat and the second flange is firmly connectable to the frame of the seat. Both flanges put together form a case clamped together by a ring.
Furthermore, the first flange is equipped with a toothed ring with the teeth directed to the inner side and on a circular slide way may freely rotate in relation to the flange.
Also this known hinge attachment is relatively material consuming and thus weighty and not very convenient to handle in the assembling process.
In view of the state of the art, it is an object of the invention to provide a casing of a hinge attachment and a method for manufacturing such an attachment, wherein the height of the toothed element is significantly bigger than the thickness of the walls of the hinge parts and the hinge parts and the toothed element form a statically compact casing unit, which has a distinctly reduced weight and simultaneously has distinctive flexible assembling characteristics, high stability under load and high accuracy.